1. Field of the Invention
The present invention relates to ink jet printers, and, more particularly, to memory usage in ink jet printers.
2. Description of the Related Art
Non-volatile memory modules are used in ink jet printers to store data such as ink usage information. Non-volatile memory modules generally retain their contents over a loss of power. However, there is nothing to prevent corruption of the data contents of the non-volatile memory if a loss of power occurs while data is being written into the non-volatile memory. Such a data corruption can be catastrophic; for example, a loss of ink usage information could destroy the printhead by firing a xe2x80x9cdryxe2x80x9d printhead. Another possibility is that a loss of the ink tank installation date could incorrectly expire a supply item earlier than it should, thus increasing the cost of supplies.
A window of opportunity exists for the corruption of memory module data, because much of the data exists in the form of multiples of discrete data values. If a power loss occurs in the middle of writing this data, data corruption will occur. For example, assume that the ink usage is stored in two bytes in the memory module. If a power loss occurs after the first byte has been written, but before the second byte has been written, the ink usage information has been corrupted.
What is needed in the art is a method of minimizing the damage to memory contents in the event that a power loss occurs during a data write operation.
The present invention provides a write fault tolerant non-volatile memory usage algorithm.
The invention comprises, in one form thereof, a method of storing usage information in an ink jet printer. Low priority usage information is stored in a first memory field. First high priority usage information is stored in a second memory field. Second high priority usage information is stored in a third memory field. The second high priority usage information is substantially identical to the first high priority usage information.
The invention comprises, in another form thereof, an ink jet printer including a memory module having a first field containing low priority usage information, a second field containing first high priority usage information, and a third field containing second high priority usage information substantially identical to the first high priority usage information.
An advantage of the present invention is that, in the event of a loss of power, usage information in a non-volatile memory is not corrupted.